The present invention is directed, in general, to tamper-evident closures for containers, and, more particularly, to closures which incorporate a tamper-evident band designed to be detached from the closure when the closure is either rotated on the container or is lifted off the mouth of the container, thereby providing visible evidence of tampering with the container.
A wide variety of container closures, both metal and plastic, have been designed for providing evidence of tampering with the containers on which they are secured, and for providing visible evidence that the container has been opened, or partially opened. Such closures generally comprise an annular body with a closed end adapted to fit over the mouth of the container, and may include a sealing mechanism for engaging the inner, top, or outside edges of the container mouth to seal the container. Some such closures utilize a security strip of some type which may be connected to the cap, and which must be removed before the cap itself can be removed from the container. Such security strips serve the purpose of providing a visible indication of tampering, but they are often difficult to use, and they are not easily or economically made. To overcome this difficulty, closures have been designed with a tamper-evident ring or band secured to the cap, such bands being designed to be broken away from the cap by rotation of the cap in the direction of opening. A large number of such designs have been produced commercially, but they have not always been totally satisfactory, since they are not always reliable, and don't always indicate the existence of, for example, a broken seal for the container, which can occur without completely opening the closure.
Many tamper-evident bands have been designed to have a plurality of vertically extending ribs which attach the band to its cap. Such bands are often designed with a degree of flexibility which allows the cap to be pressed onto the container, with the band flexing to slide over a retaining bead, so that upon removal of the cap by unthreading it, the lifting action of the cap will detach the ring, and leave it on the container. However, the lifting action caused by unthreading the closure can often unseal the container before the tamper-evident band breaks away from the cap, thereby allowing the contents to become contaminated without providing a positive indication of tampering.
Since most tamper-evident bands are designed to operate with a threaded closure, they are not always satisfactory with a lift-off (nonthreaded) cap, because the band may be too flexible, the connection between the cap and the band may be too strong to permit easy lift-off operation, or because the band fails to protect against twisting of the lift-off cap, which may break the seal between the cap and the container without fracturing the band or its connectors. Such rotation can allow contamination of the contents of the container without providing visible evidence of the damage.
Closures having tamper-evident bands which are sufficiently flexible to slide onto a container without fracturing during a capping operation may also be sufficiently flexible to allow a lift-off cap to be carefully removed without fracturing, for example, by lifting the cap by means of a lift-off tab, causing the cap to bend slightly and allowing the flexible band to be slipped over the retaining bead on the container. If the band is made sufficiently strong to prevent this from happening, as by reducing the flexibility of the band and increasing the strength of the connecting ribs which secure the band to the cap, then the closure may be too difficult for some people to open.